1. Field of the Invention
The invention relates to highly effective polarizers made from polymer products containing polyacetylene, whose matrix is a copolymer in which 70 to 90% of all comonomer units are vinyl alcohol units, the said polarizers having a high dichroic ratio Q.sub.E with a simultaneously very high degree of polarization P. Polarizers of this type are used as film.
2. Description of the Related Art
The production of polarizing films based on polyvinyl alcohol and iodine is disclosed for example in DD 210,342. In this instance, a polyvinyl alcohol film is subsequently coloured. In order to obtain results which are in any way satisfactory, a complicated production and post-treatment process is necessary. Nevertheless, as a rule only a portion of the film obtained in this manner is usable. In practice, the production of polarizing films of this type is limited to iodine and additionally only a few substances with highly effective dichroic behaviour, which limits the applicability of the said films.
Furthermore, EP 249,019 discloses improved polarizers based on polyacetylene bonded to polymer matrices. The films obtained therefrom already exhibit a good optical quality. Thus, for example, after the polymerization of acetylene in a solution of polyvinyl alcohol in DMF, a polarizing film is obtained which has a light polarizing effect of more than 90% after 4-fold stretching.
However, these films disclosed in the EP patent application mentioned still do not have a dichroic ratio which is sufficiently high for "high tech" applications, this ratio being defined as the quotient Q.sub.E of the extinction in the blocking position to the extinction in the transmitting position. The film mentioned in the exemplary embodiment of the EP patent application mentioned is reddish-brown coloured.